AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
The Effect of Particle Size, Shape, and Composition on Ice Nucleation
DAVID BELL, Jacqueline Wilson, Naruki Hiranuma, Ottmar Möhler, Harald Saathoff, Josef Beranek, Gourihar Kulkarni, Dan Imre, Alla Zelenyuk, Pacific Northwest National Laboratory
Abstract Number: 560 Working Group: Aerosols, Clouds, and Climate
Abstract Aerosol particles affect the Earth’s radiation balance directly by scattering and absorbing solar radiation and indirectly, by serving as cloud condensation nuclei (CCN) and ice nuclei (IN), thus determining properties of clouds. The relationship between the properties of aerosol particles and clouds remains the most uncertain aspect in our current understanding of climate change.
Here we present the results of recent studies, in which we applied our single particle mass spectrometer (miniSPLAT) to investigate the effect of particle size, shape, and composition on its ability to serve as ice nuclei (IN). The IN studies were conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) chamber at the Karlsruhe Institute of Technology and in our laboratory, using compact ice chamber (CIC).
The experiments in the AIDA chamber were conducted on a large number of aerosol types that include illite, kaolinite, feldspar, Saharan dust, Argentinian soil dust, soot, pollen, bacteria, cellulose, SOA-coated feldspar, sulfuric acid coated illite, feldspar, and soot, and others. Prior to cloud formation miniSPLAT was used to characterize the compositions and vacuum aerodynamic diameters (dva) of overall aerosol population and the size-dependent effective densities and dynamic shape factors of mobility- and mass-selected particles.
Following cloud formation, the compositions and dva distributions of activated and un-activated particles are characterized and compared with the overall population. Preliminary results indicate that IN residuals are larger and have slightly increased Pb content. These findings bear a close resemblance to our observations for the experiments conducted in CIC chamber on size-selected Arizona Test dust and volcanic ash particles.
Furthermore, we find that when activated, soot particles underwent a dramatic change in morphology, as the fractal particles collapsed into compact structures.